1. Field of the Invention
The present invention relates to an image recording apparatus that supports both-side recording, and more particularly, to a recording medium conveyance method executed by an image recording apparatus.
2. Description of the Related Art
For an image recording apparatus, a method for executing a recording process (data recording) on both sides of a recording medium is generally known.
For an image recording apparatus that supports both-side recording, a method for executing a recording process on the top side (a first face) of a recording medium with an image recoding unit, for re-feeding the recording medium to the image recording unit after conveying the recording medium toward a reversal path and reversing the recording medium to the back side (a second face), and for executing the recording process on the back side is known.
For example, an ink-jet color printer of a full line type is known as such an image recording apparatus. In the color printer of a full line type, recording heads, in each of which a plurality of nozzles for jetting an ink are formed in (cross feed direction) orthogonal to the conveyance direction of a recording medium, are arranged at intervals respectively for ink colors in the conveyance direction (feed direction).
In such an image recording apparatus (color printer), characters and images are recorded by feeding (supplying) and conveying a recording medium, by placing the recording medium, for which a recording process is to be executed, as opposed to a plurality of ink nozzles in each nozzle array (recording head), and by jetting inks of respective colors onto a recording medium being conveyed.
Additionally, since one image recording unit makes recording on the first and the second faces of a recording medium in such an image recording apparatus, the recoding medium is again conveyed to the image recording unit via a reversal path after the first face of the recording medium is recorded. In such an image recording apparatus, however, a succeeding recording medium can possibly collide with a preceding recording medium on a conveyance path unless timing at which a recording medium is conveyed when its first face is to be recorded, and timing at which the recording medium is conveyed when its second face is to be recorded by being re-fed are optimally controlled.
As a method for preventing this collision, a method for widely securing a distance (a page gap) between preceding and succeeding recording medium is known.
However, widely securing a page gap reduces the number of sheets recorded per unit time of an image recording apparatus, leading to degradation in a throughput.
For example, Patent Document 1 (Japanese Published Unexamined Patent Application No. 2006-131415) discloses a method for deciding the supply timing of a succeeding recording medium by making scheduling for satisfying all of first, second and third conditions to be descried below as a technique for setting a page gap.
the first condition: The conveyance start timing of a recording medium (A) to be fed to an image recording unit in order to make recording on the first face of the recording medium, and the conveyance start timing of a recording medium (B) to be re-fed to the image recording unit in order to make recording on the second face are decided when the front edge of the recording medium B reaches a collection unit while maintaining a page gap upon completion of the passage of the recording medium A.
the second condition: The supply timing is decided when the front edge of a succeeding recording medium reaches a supply position while maintaining a page gap of a predetermined amount or more at the timing when the preceding and the succeeding recording medium do not exist at the same time in the supply position of a recording medium on a more upstream side than an image recording unit for executing a recording process for a recording medium, and the rear edge of the preceding recording medium has passed.
the third condition: The supply timing is decided when the front edge of a succeeding recording medium reaches a reversal position while maintaining a page gap of a predetermined amount or more at the timing when the preceding and the succeeding recording medium do not exist at the same time in the reversal position in a path switching unit, and the rear edge of the preceding recording medium has passed.
According to Patent Document 1, an image recording apparatus for setting a required minimum page gap of a succeeding recording medium 43b from a preceding recording medium 43a, and for executing a continuous recording process with nozzle arrays (recording heads) 41 is realized.
However, with the scheduling method according to Patent Document 1, a path switching unit 42 is controlled by making switching with a page gap in each of a both-side continuous recording process, and a both-side/one-side continuous recording process.
Here, the page gap of Patent Document 1 is described with reference to FIG. 1.
FIG. 1A shows the conveyance of recording medium at the time of one-side continuous recording, whereas FIGS. 1B and 1C show the conveyance of recording medium at the time of both-side continuous recording or at the time of one-side/both-side continuous recording.
For the page gap of Patent Document 1, a page gap at the time of one-side recording is assumed to be t, and a page gap at the time of both-side continuous recording and at the time of both-side/one-side continuous recording is assumed to be t+α. Additionally, the succeeding recording medium 43b is conveyed after the preceding recording medium 43a by widening the distance by the page gap of α at the time of both-side continuous recording and at the time of both-side/one-side continuous recording. The reason why the distance is widened by the page gap of α is that the page gap must be secured by an excess of α since a process for moving the path switching unit 42 by h during a transition from FIG. 1B to FIG. 1C at the time of both-side continuous recording or at the time of both-side/one-side continuous recording.
Therefore, the page gap becomes wide by α at the time of both-side recording or at the time of both-side/one-side recording in comparison with a page gap at the time of one-side recording.